ExternalInput Identifies parameters of an RemoteCallable that will be pulled from the caller of the callback. 
RemoteCallable Used to tag a method as callable using CallbackReceiver.createRemoteCallback(Context)


CallbackHandlerRegistry.CallbackHandler<T extends CallbackReceiver> The interface used to trigger a callback when the pending intent is fired. 
CallbackReceiver<T> An objects that can receive remote callbacks. 


AppWidgetProviderWithCallbacks<T extends CallbackReceiver> Version of AppWidgetProvider that implements a CallbackReceiver
BroadcastReceiverWithCallbacks<T extends CallbackReceiver> Extend this broadcast receiver to be able to receive callbacks as well as normal broadcasts. 
CallbackHandlerRegistry The holder for callbacks that are tagged with RemoteCallable
ContentProviderWithCallbacks<T extends ContentProviderWithCallbacks> Version of ContentProvider that can be used as a CallbackReceiver
RemoteCallback An instance of a callback to a specific class/method with a specific set of arguments.